Vehicle turn signals are a valuable safety device because they signal to other vehicles a driver's intention to make a left or right turn. These devices are equipped with mechanical structures which detect when a turn has been completed by sensing the occurrence of a sufficient rotation of the steering wheel which is normal for a completed turn.
On occasion, however, a driver may be observed proceeding down a street or highway with no intention of turning, but with a turn signal flashing. Such erroneous signalling may be both an irritation to other drivers and a safety hazard to drivers who may depend upon the signalling driver's intentions when choosing the path of their own vehicle.
Erroneous signals can arise from a variety of causes. A driver may actuate the turn signals and then change his or her mind without remembering to deactuate the turn signal. On some occasions, a turn is of such a small angle that the signal's turn sensing mechanisms do not deactuate the signalling device. False signalling also commonly occurs by safety conscious drivers who signal lane changes on a highway, but forget to deactuate their turn signal when they return to their desired lane.
A variety of circuits have been proposed to provide an alarm signal to warn a driver that a turn signal may have been inadvertently left actuated. Such circuits are, for example, found in the following U.S. Pat. Nos.: 3,445,810; 3,806,868; 3,964,019; 4,241,328; 4,792,785; 4,907,844; 4,924,208; and 4,933,665.
Despite the existence of these proposals, turn signal reminder circuits have not been accepted either as retrofit, after-market equipment or as original equipment. The reasons for this may include that some of the alarms have circuitries which are too complicated, have too many parts, and therefore are both too expensive and physically too large for inclusion in the conventional flasher can or for easy connection to existing vehicle signalling circuitry. Additionally, some of the alarms may be too obtrusive and therefore irritating to the vehicle operator.
It is therefore an object and feature of the present invention to provide a turn signal reminder circuit which may be installed to a conventional flasher can connector with a minimum of additional connection required to other circuitry and which is sufficiently simple, small and inexpensive that its inclusion either in new vehicles or its addition to existing vehicles is convenient and practical.
Another object and feature of the present invention is to provide a turn signal reminder circuit which sounds its alarm in synchronism with the existing flasher and does so only during relatively shorter time intervals, separated by relatively longer time intervals so as to provide a sufficient, but not annoying alarm to the vehicle's operator.